Grantee Research Project Results
Final Report: Biobeds for Containment and Destruction of Pesticides at Agricultural Mixing and Loading Facilities
EPA Contract Number: 68D00236Title: Biobeds for Containment and Destruction of Pesticides at Agricultural Mixing and Loading Facilities
Investigators: Lamar, Richard T.
Small Business: EarthFax Development Corporation
EPA Contact:
Phase: I
Project Period: September 1, 2000 through March 1, 2001
Project Amount: $69,683
RFA: Small Business Innovation Research (SBIR) - Phase I (2000) RFA Text | Recipients Lists
Research Category: SBIR - Pollution Prevention , Pollution Prevention/Sustainable Development , Small Business Innovation Research (SBIR)
Description:
Problem:
Although groundwater contamination by pesticides is largely
attributed to non-point sources, pesticide contamination of soil
and
groundwater at agrochemical dealerships (Mueller 1989), pesticide
mixing/loading sites (Hallberg 1985) and pesticide applicator cleaning sites
(Kruger and Seiber 1984) indicates that point sources are also significant
sources of groundwater contamination. Indeed, agrochemical storage and handling
practices have been targeted as a ?point source? for potential groundwater
contamination by federal and state legislation across the United States (Kammel
and Walsh 1989). Evaluation of soils and groundwater for pesticide contamination
at a variety of pesticide mixing/loading sites indicates that these sites are a
point source of contamination and possess the potential for future contamination
unless preventative measures are taken. The pesticides found in groundwater at
agrochemical handling facilities are, in general, those most frequently used. A
summary of data from studies that evaluated frequencies with which different
pesticides have been detected in ground water beneath agrochemical handling
facilities in Wisconsin and Illinois indicated that the five most frequently
detected pesticides-atrazine, alachlor, metolachlor, cyanizine and
metribuzin-were also those used most extensively by the facilities included in
the study (Barbash and Resek 1996).
The installation of well designed,
agrochemical handling facilities referred to as chemical mixing centers (CMCs)
or chemical mixing facilities (CMFs) has been proposed by several groups to
prevent soil and groundwater contamination associated with improper handling of
pesticides (Carter 1994, Wilson 1994, Dwinell 1994). The costs for these
engineered facilities have been reported to range from $8,500.00 (Wilson 1994)
to $20,000 (Carter 1994) and as high as $40,000 (personal communication with Mr.
Michael Broder, National Fertilizer & Environmental Research, Tennessee
Valley Authority 1999). The expense of these facilities may be cost prohibitive
to the majority of the 1.4 M farms where pesticides are used because of the low
net incomes generated by those farms.
Solution:
If pesticide users,
the vast majority of who are members of the agriculture community, are to be
convinced to adopt practices that prevent pesticide contamination of groundwater
at mixing/loading facilities, less expensive alternatives need to be offered.
One such alternative that is simple in design, easy and inexpensive to maintain,
employs inexpensive materials that are readily available to farmers and that is
based on the microbial degradation of pollutants is the concept of biobeds. A
biobed is an in-ground treatment unit designed to contain spills of herbicides
and other pesticides, even of high doses on limited surfaces, and to destroy the
chemicals, through microbiological activity, as rapidly as possible (Torstensson
and Castillo 1997). In its simplest form, a biobed is a rectangular excavated
hole in the ground (60 cm deep and 0.5 m broader and longer than the sprayer
tank or other mixing container) filled with a mixture of top soil and readily
available organic amendments such as peat and straw.
Objectives:
The
primary objective of the Phase I work was to evaluate the technical feasibility
of using biobeds to contain and destroy pesticides at pesticide mixing and
loading facilities in the United States. To achieve this objective, the
following technical questions were addressed:
- What is the degradative potential of biobeds towards individual pesticides
and pesticide mixtures
commonly used in the United States? - Can substrates, readily available in areas of high pesticide use, be
substituted for straw without
loss of pesticide degradation performance. - What is the contribution of leaching to decreases in pesticide concentrations within the biobed?
- Is there a benefit to biobed performance from inoculation of the biobed
mixture with white-rot fungi.
The technical potential of using biobeds to contain and degrade pesticides was evaluated in a series of experiments using
laboratory-scale biobeds located in greenhouses. In general, experiments involved application(s) of the selected herbicides to the surface of the biobeds that were prepared to assess the various factors (e.g. various substrate mixtures; with and without fungal inoculation) . The herbicide-degrading potential of the biobed substrate mixtures was determined by analyzing soil/peat/(straw or corn stover or corn cob) mixture sub-samples taken from various depths in the beds to determine residual herbicide concentrations over time.
Experiments:
A total of three experiments were conducted to evaluate the herbicide degrading performance of the biobeds. The herbicides
evauated were: atrazine, acetochlor, alachlor and metolachlor. In Experiment #1, the herbicide-degrading performance of a
soil-substrate mixture containing 25% (by volume) top soil, 25% peat moss and 25% straw (Mixture A), which was used by
Torstensson and del Pilar Castillo (1997), was evaluated. In this work barley straw was used in place of wheat straw. In Experiment #2 the effect of replacing barley straw with corn husks or corn stovers on the herbicide-degrading performance of the biobeds was evaluated. The effect of white-rot fungal inoculation on the herbicide-degrading performance of soil-substrate Mixture A was evaluated in Experiment #3. Biobed herbicide-degrading performance was assessed by determining the concentrations of herbicides, initially applied to the surface of the biobeds, at the following depths: 0-5 cm, 5-15 cm, 15-30 cm, 30-45 cm and 45-60 cm.
Summary/Accomplishments (Outputs/Outcomes):
The modification of the original soil-substrate mixture developed by Torstensson and co-workers (Torstennson and Castillo 1997)., with wheat straw substituted with barley straw, had a very high capacity for the degradation of the tested herbicides as evidenced by their half-lives (T1/2) under the various tested biobed conditions (Table 1).. The half-lives of the herbicides obtained in this study were either much lower, in the case of atrazine, or well within the ranges of literature reported half-lives for the same herbicides (Table 2). The initial herbicide concentrations in the 0 to 5 cm surface layer that were evaluated in this work were, in some cases, three orders of magnitude greater than pesticide residue concentrations reported by Torstennson and Castillo (1997) during the spraying season. Despite these high initial concentrations (e.g. > 1000 mg kg-1) the degradation of all the tested herbicides was rapid and extensive.Table 1. Half-lives (T1/2)1 of the tested herbicides in the upper 0 to 5 cm layer in biobeds.
Atrazine | Acetochlor | Alachlor | Metolachlor | |||||
Soil-Substrate | (T1/2-days) | |||||||
Mixture | ||||||||
Experiment #1 | ||||||||
|
2.2 | 5.5 | 27.3 | 29.6 | ||||
Experiment #2 | ||||||||
|
4.8 | 14.9 | ||||||
|
7.3 | 17.5 | ||||||
|
8.6 | 9.8 | ||||||
|
2.7 | 16.9 | ||||||
Experiment #3 | ||||||||
|
0.62 | 27.8 | ||||||
|
0.14 | 27.3 | ||||||
|
1.89 | 27.1 | ||||||
|
1.02 | 26.8 |
1Half-lives were determined using least squres plots of log (Y) =
a + b(x)0.5, where Y equals the concentration of herbicide in mg
kg-1 and X equals time in days.
2All mixtures were
composed of 25% top soil and 25% peat moss (by volume). The bulk was made up of:
Mixture A 50% barley straw; Mixture B 50% corn stovers; Mixture C 50% corn
cobs
3Overall = overall soil-substrate mixture
treatments.
4Overall = overall fungal treatments (i.e. including
the non-inoculated treatment).
The chloroacetanilide herbicides (e.g.
alachlor, acetochlor and metolachlor) are generally known to degrade more
quickly in the soil than triazine herbicides, including atrazine (Scribner et
al. 2000)., with typical half-lives for the chloroacetanilides ranging from 15
to 30 days (Leonard, 1988)., compared to 30 to 60 days for triazines (Ferrer et
al., 1997). This is contrary to the rates of disappearance observed in this work
for the herbicides in the biobeds with atrazine degradation equaling or
exceeding the rate and extent of degradation of the most labile
chloroacetanilide, acetochlor (Table 1).. Therefore, the microbial communities
that were produced in the biobeds appeared to be particularly suitable for
atrazine degradation.
Table 2. Reported half-lives for atrazine,
acetochlor, alachlor and metolachlor.
Atrazine | Acetochlor | Alachlor | Metolachlor | Reference |
15-54 | 36-71 | Topp et al., 1994 | ||
50-265 | Obrador et al., 1993 | |||
37 | Jenks et al. 1998 | |||
31-54 | 15-77 | Workman et al., 1995 | ||
5-8 | 4-8 | 9-19 | Mueller et al., 1999 | |
9-11 | 17-23 | Zimdahl and Clark, 1982 | ||
11-14 | Braverman et al., 1986 | |||
11-24 | 39-70 | Walker and Brown, 1985 | ||
8 | Beestman and Deming, 1974 | |||
20-39 | Jurado-Exposito and Walker,1998 | |||
14-31 | Guo and Wagenet, 1999 | |||
18 | Sanyal and Kulshrestha, 1999 | |||
24 | Weed et al., 1995 | |||
18-45 | Walker et al., 1992 | |||
6 | Wienhold and Gish, 1994 | |||
20-40 | Walker and Welch, 1991 | |||
7-20 | Jones et al., 1990 |
As had been observed in previous soil studies (Jenks et al., 1998), the rate
of atrazine degradation decreased with increasing
soil-substrate mixture
depth. However, even at the lower soil-substrate mixture depths (i.e. 30 to 45
cm and 45 to 60 cm), atrazine degradation was extensive. The half-lives for
atrazine that were observed in Experiments #?s 1 and 3 (Table 1) are extremely
short compared to those reported in the literature (Table 1). Initial atrazine
concentrations in the biobed experiments were in the range of 1000 mg kg-1 in
Experiment #1 and as high as approximately 7000 mg kg-1 in Experiment #3. This
is much higher than surface soil concentrations that result from atrazine field
applications that are in the single digit mg kg-1 (Workman et al., 1995).
Atrazine concentration over the range of 5 to 5000 mg kg-1 did not affect the
rate of degradation (Gan et al., 1996). Thus, the greater rates of degradation
were probably due to the active microbial population produced in the biobeds
rather than increased degradation as a result of higher initial atrazine
concentrations.
Persistence of chloroacetanilide herbicides in the field
soils widely depending on soil type, temperature, soil water, and depth below
the soil surface (Kotoula-Syka et al., 1997). Metolachlor is the most persistent
acetanilide (Walker and Brown, 1985; Zimdahl and Clark, 1982) and had a average
half-live (13.7 days) in three soils that was approximately two times as long
those observed for alachlor and acetochlor (Mueller et al., 1999). This is
similar to what we observed in the biobeds. The average half-life of metolachlor
(27.7 days) was 1.7 times and 4.8 times longer than the average biobed
half-lives of alachlor and acetochlor, respectively. Alachlor degradation in
soil was enhanced by the addition of manure (T1/2 = 21.8 days) and alfalfa (T1/2
= 14.4 days) compared to unamended soil (T1/2 = 24.9 days) (Guo and Wagenet,
1999). The authors speculated that although both manure and alfalfa would
enhance alachlor adsorption, the increased supply of nutrients associated with
the substrates, compared to unamended soil, probably stimulated microbial growth
and, therefore, the rate and extent of alachlor degradation. Alachlor was
degraded more rapidly in biobed soil-substrate mixtures containing corn stovers
(T1/2 = 9.8) compared to soil-substrate mixtures containing barley straw (T1/2 =
17.5 days) or corn cobs (T1/2 = 16.0 days) (Table 8). Corn stovers have a higher
protein, and thus greater nitrogen content than either barley straw or corn
cobs. Thus, the enhanced nutrient status in the soil-substrate mixtures
containing corn stovers may have been indirectly responsible for the decrease in
alachlor persistence compared to soil-substrate mixtures containing either
barley straw of corn cobs. However, acetochlor degradation was most rapid in
soil substrate mixtures containing corn cobs, not corn stovers.
Degradation of all of the tested herbicides was rapid and extensive.
Although there was some evidence of herbicide leaching from upper to lower
depths in the soil-substrate mixtures, there was no accumulation of any of the
herbicides at any depth. As expected, degradation of the barley straw, corn
stovers and corn cobs occurred to varying degrees. Degradation of the barely
straw and corn stovers was the greatest and resulted in about a 15 to 25 cm
decrease in total biobed depth. Corn cobs, did not degrade as much, resulting in
much less of a decrease in total biobed depth. The ability of a substrate to
support herbicide degradation and maintain biobed depth over time is an
important consideration in biobed maintenance (i.e. frequency of substrate
replacement). Biobeds appear to be a technically sound alternative for
containment and degradation of pesticides at mixing and loading facilities.
References:
1. Barbash, J. E. and E. A. Resek. 1996. Chapter 8 pp. 323-334. In:
Pesticides in Groundwater-
Distribution, Trends and Governing Factors.
Chelsea, MI Ann Arbor Press.
2. Beestman, G. B. and J. M. Deming. 1974.
Agron. J. 66:308-311.
3. Braverman, M. P., T. L. Lavy, and C. J. Barnes.
Weed. Sci. 34:479-484.
4. Carter, R. V., Jr. 1994.. pp. 199-202. In:
(Campbell, K. L., W. D. Graham, and A.B. Bottcher, eds.)
Environmentally
Sound Agriculture Proceedings of the Second Conference, Orlando, FL. ASAE.
5.
Dwinell, S. E. 1994. pp. 152-155. In: Conference Proceedings Pesticide and
Fertilizer
Containment Symposium. Midwest Plan Service MWPS-C2.
6. Gan,
J., R. L. Becker, W. C. Koskinen, and D. D. Buhler. 1996. J. Environ. Qual.
25:1064-1072.
7. Guo, L. and R. J. Wagenet. 1999. Soil Sci. Soc. Am. J.
63:443-449.
8. Hallberg, G. 1985. North Centeral Weed Control Conf.
Proceedings 40:130-147.
9. Jenks, B. M., F. W. Roeth, A. R. Martin, and D. L.
McCallister. 1998. Weed Sci. 46:132-138.
10. Jones, Jr., R. E., P. A. Banks,
and D. E. Radcliffe. 1990. Weed Sci. 38:589-597.
11. Juardo-Exposito, M. and
A. Walker. 1998. Weed Research 38:309-318.
12. Kotoula-Syka, E., K. K.
Hatzios, D. F. Berry, and H. P. Wilson. 1997. Weed Technol. 11:403-409.
13.
Mueller, W. 1989. Dealers at the source. Agrichem. Age 33:10-12.
14. Mueller,
T. C., D. R. Shaw, and W> W> Witt. 1999. Weed Technology
13:341-346.
15. Krueger, R. F. and J. S. Seiber. 1984. Symposium Series 259,
American chemical society,
Washington, D.C. pp. 368.
16. Obrador, A., Y.
Lechon, and L. Tadeo. 1993. Pestic. Scie. 37:301-308.
17. Sanyal, D. and G.
Kulshrestha. 1999. Biol. Fertil. Soils 30:124-131.
18. Scribner, E. A., E. M.
Thurman, and L. R. Zimmerman. 2000. Sci. Total Environ. 248:157-167.
19.
Topp, E., W. N. Smith, W. D. Reynolds, and S. U. Khan. 1994. J. Environ. Qual.
23:693-700.
20. Torstensson, L. and M. d. P. Castillo. 1997. Pest. Outlook
June:24-27.
21. Walker, A. and S. J. Welch. 1991. Weed. Res. 31:49-57.
22.
Walker, A. and P. A. Brown. 1985. Bull. Environ. Contam. Toxicol.
34:143-149.
23. Walker, A., Y. H. Moon, and S. J. Welch. 1992. Pestic. Sci.
35:109-116.
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Pfeiffer. 1995. J. Environ. Qual. 24:68-79.
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Gish. 1994. J. Environ. Qual. 23:292-298.
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184-190. In:Enviornmentallyt sound Agriculture. Proceddings of the 2nd Conf.
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Conclusions:
- The degradative performance of biobeds toward several of the most commonly
used herbicides in the
U.S. was exceptional,. particularly for the most heavily used herbicide in the U. S., atrazine. Indeed,
the ability of biobeds to degrade herbicides, as demonstrated by Torstensson and co-workers and in
the work reported here, suggests that they might also be useful for remediation of pesticide-
contaminated soils.
- Substitution of barley straw with either corn stovers or corn cobs had no
effect or enhanced the
herbicide-degrading performance of biobeds. Therefore, all three of these readily available and
inexpensive agricultural residues can be used as substrates in biobeds.
- Herbicide leaching within the biobeds was not a factor. Herbicide that
leached from upper to lower
levels was degraded over time with the result that there was no accumulation of herbicide at lower
levels in the biobeds.
- Inoculation of biobeds with two species of WRF did not significantly enhance
degradation of the
herbicides evaluated in this work. However, with the wide variety of pesticides used, future use of
WRF to enhance herbicide degradation in biobeds should not be ruled out.
Supplemental Keywords:
Pesticide containment, pesticide soil remediation, biostimulation., RFA, Scientific Discipline, Toxics, Waste, Ecosystem Protection/Environmental Exposure & Risk, Sustainable Industry/Business, Chemical Engineering, Ecosystem/Assessment/Indicators, Ecosystem Protection, Chemical Mixtures - Environmental Exposure & Risk, Environmental Chemistry, cleaner production/pollution prevention, pesticides, Chemistry, Ecological Effects - Environmental Exposure & Risk, chemical mixtures, Analytical Chemistry, Ecological Effects - Human Health, Chemistry and Materials Science, Agronomy, Engineering, Environmental Engineering, Ecological Indicators, Agricultural Engineering, pesticide exposure, agricultural environments, agricultural mixing/loading , agriculture, agrochemcial, biobeds, agricultural chemical applicationThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.